1. Field of the Invention
The present invention relates to a magnetic recording medium including a recording layer formed in a predetermined concavo-convex pattern in which recording elements for recording information are formed as convex portions thereof.
2. Description of the Related Art
Conventionally, various types of development such as miniaturization of magnetic particles forming a recording layer, change of a material of the magnetic particles, and improvement of fine head processing have been made for magnetic recording media such as hard discs in order to largely improve the areal density of the recording layer. The improvement of the areal density is expected to continue.
However, many problems including the limitation of the head processing, erroneous information recording to a track adjacent to a target track caused by broadening of a magnetic field, crosstalk during reproduction, and the like are made apparent. This means the improvement of the areal density by the conventional development approaches has already reached the limit. Magnetic recording media such as discrete track media and patterned media, in which a recording layer is formed in a predetermined concavo-convex pattern and recording elements for recording information are formed as convex portions of the concavo-convex pattern, have been proposed as prospective magnetic recording media capable of further improvements in areal density (see Japanese Patent Laid-Open Publications Nos. Hei 10-222944 and Hei 9-97419, for example). In those magnetic recording media, it is considered that the side faces of the recording element that are approximately perpendicular to a surface thereof are preferable, as described in Japanese Patent Laid-Open Publication No. Hei 10-222944, for example.
Erroneous information recording to a track adjacent to a target track, crosstalk and the like can be suppressed by recording information to the recording elements formed as the convex portions.
On the other hand, in the case where the surface of the magnetic recording medium is formed in a concavo-convex pattern, the flying height of a head is unstable. This may degrade the recording and reproduction characteristics. Thus, it is preferable to planarize the surface of the magnetic recording medium by depositing a non-magnetic material on the recording layer of the concavo-convex pattern so that concave portions between the recording elements are filled with the non-magnetic material and then removing the excess non-magnetic material on the recording elements. Moreover, the side face of the recording element can be easily damaged by processing. The damage of the side face may degrade the magnetic characteristics. When the damage of the side face of the recording element is left as it is, corrosion or oxidization caused by moisture,
oxygen in the air or the like may progress to further degrade the magnetic characteristics. However, when the non-magnetic material comes into close contact with the side face of the recording element, contact of moisture, oxygen or the like with the side face of the recording element can be suppressed. For this reason, filling the concave portions between the recording elements with the non-magnetic material is preferable.
Dry etching can be used for processing the recording layer in a concavo-convex pattern. Various dry etching methods have been developed in order to process the side faces of the convex portions of the concavo-convex pattern to be approximately perpendicular to the surfaces of the convex portions. Moreover, deposition techniques used in the art of semiconductor manufacturing, such as sputtering, can be used for depositing the non-magnetic material. In addition, process techniques used in the art of semiconductor manufacturing, such as CMP (Chemical Mechanical Polishing), can be used as a technique for removing the excess non-magnetic material on the recording layer to planarize the surface of the recording layer and non-magnetic material.
However, it is difficult to completely fill the concave portions between the recording elements with the non-magnetic material even when the non-magnetic material is deposited on the recording layer of the concavo-convex pattern by the above technique. That is, voids are often formed in the concave portions. Such voids may allow for entrance of moisture, air, or the like thereto. The entering moisture, air, or the like cause corrosion or oxidization of the side faces of the recording elements, which may degrade the magnetic characteristics.